Switch sparse set to use unsigned size_t.

include/sprs.h

@@ -58,7 +58,7 @@ struct sprs_s {
    * The dense array.
    * This is a pointer so that an array of a certain size can be allocated as needed.
    */
-  int* dense;
+  size_t* dense;
   /**
    * The sparse array.
    * This is a pointer so that an array of a certain size can be allocated as needed.
@@ -94,14 +94,14 @@ void sprs_free(sprs* sprs);
  * @param index the index at which to store the value
  * @param data the value to store.
  */
-void sprs_put(sprs* sprs, int index, void* data);
+void sprs_put(sprs* sprs, size_t index, void* data);
 /**
  * Checks if the sparse set contains data under a given index.
  * @param sprs the sparse set to check.
  * @param index the index for which to check.
  * @return 1 if the index exists, 0 if not.
  */
-int sprs_contains(sprs* sprs, int index);
+int sprs_contains(sprs* sprs, size_t index);
 /**
  * Gets the value stored under the given sparse set index.
  * This will check for whether the index is in the sparse set first,
@@ -113,7 +113,7 @@ int sprs_contains(sprs* sprs, int index);
  * @param index the index from under which to retrieve the value.
  * @return the value stored under the index, or NULL if there is nothing there.
  */
-void* sprs_get(sprs* sprs, int index);
+void* sprs_get(sprs* sprs, size_t index);
 
 /**
  * Runs through every element in the sparse set, and compares it against the